As a successor of W-CDMA and HSDPA, a communications method called Evolved UTRA (E-UTRA) has been under considerations. E-UTRA is a radio access method that extendably supports plural bandwidths, and responds to a bandwidth from 1.25 MHz up to 20 MHz while assuring compatibility with an existing 3G system.
In the existing W-CDMA, a preamble of a random access channel used to establish an initial connection in uplink, which is one of contention-based channels, is transmitted by a combination of code-multiplexing and time-multiplexing.
For example, when users are multiplexed by code-multiplexing, a terminal device can choose any signature from plural prepared signatures (codes), as shown in FIG. 1A.
In addition, when the users are multiplexed by time-multiplexing, the terminal device can chose any access slot from plural prepared access slots, as shown in FIG. 1B.
W-CDMA random access is described in Non-patent Publication 1.
Non-patent Document 1: “Advanced Digital Mobile Communications”, edited by Keiji Tachikawa, Kagaku-shimbun-sha., pp. 130-134.